On Jul 12, 2021, Christoph Müllner <cmuell...@gcc.gnu.org> wrote: > * Why does the generic by-pieces infrastructure have a higher priority > than the target-specific expansion via INSNs like setmem?
by-pieces was not affected by the recent change, and IMHO it generally makes sense for it to have priority over setmem. It generates only straigh-line code for constant-sized blocks. Even if you can beat that with some machine-specific logic, you'll probably end up generating equivalent code at least in some cases, and then, you probably want to carefully tune the settings that select one or the other, or disable by-pieces altogether. by-multiple-pieces, OTOH, is likely to be beaten by machine-specific looping constructs, if any are available, so setmem takes precedence. My testing involved bringing it ahead of the insns, to exercise the code more thoroughly even on x86*, but the submitted patch only used by-multiple-pieces as a fallback. > * And if there are no particular reasons, would it be acceptable to > change the order? I suppose moving insns ahead of by-pieces might break careful tuning of multiple platforms, so I'd rather we did not make that change. -- Alexandre Oliva, happy hacker https://FSFLA.org/blogs/lxo/ Free Software Activist GNU Toolchain Engineer Disinformation flourishes because many people care deeply about injustice but very few check the facts. Ask me about <https://stallmansupport.org>
